Composite antenna



NOV. 17, cH

COMPOSITE ANTENNA Filed Oct. 31, 1967 r v 4 Sheets-Sheet 1 FIG?! l v 17f"; "K 1L 5/16 1; 22 20 g 5%8 I I I Y B I I: CE I I; -/-L, I I 21 v 1e 1I 4 23 1s a c -////////7 s 14 F1 11 I 12 13 o I N V 1970 J. CHEILLAN3541556 COMPOSITE ANTENNA Filed Odt. 31, 1967 I 4 Sheets-Sheet 2 ,5 5 M1 a I g 3, 15

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JE (I 4M 4 mwvey S United States Patent U.S. Cl. 343727 12 ClaimsABSTRACT OF THE DISCLOSURE Composite antenna comprising in a singlestructure two units for transmitting two very different wavelengths,with a beam antenna about 1 4 in length for transmittingthe wave ofgreater wavelength A having an end fixed to an antenna set-updimensioned for transmitting the wave of similar wavelength The presentinvention relates to a device comprising fixed combined antennas forradiating energy in diverse wavebands.

The device according to the invention comprises a combination of twoantennas interconnected in a fixed manner so that each will transmit inone of two very different ranges of wavelength.

The application of an antenna combination of this nature answers avariety of practical problems, by way of example, the case of ashipwrecked survivor floating at sea on a lifesaving craft which isequipped with transmitters operating on two frequencies, one F being ofthe order of 8 megacycles (wavelength A, of approximately 38 meters)intended to permit detection up to a distance of the order of 1,250miles approximately, and the other F being of the order of 240'megacycles (wavelength A of approximately 1.25. meters) for radiolocation up to a distance of the order of approximately 95 miles. Thetwo transmitters may be arranged to operate at the same time or inalternate sequence.

In order to minimize the bulk, weight and complexity of such a set, aswell as the effort required for its assembly by a physically weakenedsurvivor, it is of importance that the antennas should form amechanically rigid unit, which should be simple to place in operation.The power applied by means of a battery or of a hand-driven generatorbeing very low, it is necessary moreover that the output of effectivelytransmitted power should be as high as possible, meaning that the twoantennas should have optimum transmission qualities.

According to the invention, a device consisting of fixed combinedantennas organized to operate on two very different wavelengths A and Awith the former considerably greater than the latter, comprises at leastone antenna section which has a length of the order of a quarter of 1for transmission of the longer wavelength A connected through the otherextremity from the unattached extremity to a device dimensioned fortransmission of the shorter wavelength x According to another feature ofthe invention, in the case of a vertically polarized, relatively longwavelength and of a horizontally polarized, relatively short wavelength,the base of the aforesaid section carries a symmetrical-asymmetricalpassage device of the balancing unit type, which feeds two antennasections each of which has a length of approximately a quarter of theshorter wavelength A According to'another feature of the invention, thepower at the high frequency F is applied to a co-axial input terminal ofthe aforesaid balancing unit through a first transformer winding, andthe power at the lower frequency F is applied through a winding of asecond transformer connected between a ground potential zone and a pointof the circuit of the said first transformer winding.

According to another feature, in the case of identical polarization, atleast one antenna section is incorporated of an overall length equal toapproximately one quarter of A whose base is connected to a hollowco-axial conductor short-circuited at the base and of a length close toa quarter of-M, the length of the said antenna section projecting out ofthe hollow conductor preferably being equal to an odd number ofquarter-waves of the shorter wavelength A The invention will now bedescribed in detail with reference to the accompanying drawings, whichillustrate several embodiments of the invention, but in no restrictivesense.

FIG. 1 is a diagrammatic illustration of one embodiment of the inventionproviding for radiation of waves of different polarization, beingvertical for the frequency F and horizontal for the frequency F FIG. 2illustrates another embodiment providing for vertical polarization forboth Waves.

FIG. 3 illustrates another embodiment providing for horizontalpolarization for both waves.

FIG. 4 illustrates an embodiment of the invention wherein the ratiobetween the two Wavelengths is 2:1.

In FIG. 1, a VHF transmitter 11 feeds power at the frequency F through atransformer 12, and an HP transmitter 13 feeds power at the frequency Fthrough a transformer 14 to the antenna arrangement in accordance withthe present invention.

This antenna arrangement comprises a short length of co-axial lead 23,Whose length C is not of a critical nature, which co-axial lead projectsinto an asymmetrical-symmetrical passage device 16 of the knownbalancing unit type, shown in section. The passage device 16 comprises acylindrical metal casing 20 axially containing a length of co-axial lead21, made up of an inner wire 21i and of an outer conductor 21e, with abase member 22 Welded to the extremity of the inner wire 21i. A sectionof antenna 17, of the whip type, which has the length A, is welded orotherwise secured to the outer side of the short terminal side of thecasing 20.

A ground potential zone is shown at 15. In the particular case ofseaborne craft, this zone may consist of a metal plate conductivelylinked with the sea.

Within the casing 20, an antenna section 18 extending horizontally andhaving a length of one-quarter of A is connected to the extremity of theouter conductor 21e of the lead 21, whereas another antenna section 18positioned co-extensively with the antenna section 18, is connected tothe inner wire 21i of the lead 21. The total internal length B of thecasing 20 is of the order of one-half of A the segment of co-axial lead21 and the base member 22 each having a length close to one-quarter of kThe HF antenna is formed by the external surface of the lead 23, theouter surface of the casing 20, and the outer surface of the antennasection 17. The overall length C+B+A of the HF antenna is of the orderof one-quarter Of 7\ The current at the frequency F drawn from thesecondary winding 12s of the transformer 12 encounters a substantiallyzero impedance at the input terminal 231' of the co-axial lead 23 andreturns on the outer surface of the outer conductor 23e. No current atthe frequency F can penetrate inside the casing 20. Thus, the VHFquarterwave sections 18 and 18' being energized by currents flowinginside the casing 20, decoupling between the two frequencies is almosttotal; and, there is no unfavorable reaction of any kind of one antennaagainst the other,

since each is dimensioned independently for its own emission at the mostfavorable value.

Below the ground potential zone 15, the co-axial lead 23, consisting ofthe inner conductor 23i and the outer conductor 23c, has its extremity23i energized at the frequency F by the secondary winding 12s of thetransformer 12. The transformer 14 energizes the whip antenna 17 at thefrequency F through its secondary winding 14s, connected ot the groundpotential zone on the one hand, and to the outer conductor 23s of theco-axial lead 23 on the other hand. It is apparent therefore that thetwo transmitters may operate simultaneously under optimum conditions ofradiation.

FIG. 2 applies to an embodiment of the invention providing polarization.The reference numerals 11 to represent similarly designated elements inthe system illustrated in FIG. 1. A hollow conductor 31, whose length Bis close to one-quarter of k is positioned vertically above the groundpotential zone 15 and is insulated from the same at its lower closedextremity 31!), the upper extremity being open. A cylindrical conductor32 connected to the lower extremity 31b is positioned along the axis ofthe hollow conductor 31. Its upper extremity 32s extends into a verticalsection 33 forming a whip antenna having the length A. The length A+B isclose to a quarter of A Energization is applied to the base 31b of theconductor 31 through a wire 34 which, by means of a reversing switch 35,may be connected either to a terminal of the secondary winding 12s oftransformer 12 or to a terminal of the secondary winding 14s oftransformer 14. These two secondary windings have their other terminalsconnected to ground.

At the frequency F the impedance of the co-axial cavity formed by theconductors 31 and 32 is infinite or at least very high, since thiscavity represents a shorted quarter-wave at this frequency. The currenthaving the frequency F which could reach the section 33 encounters aninfinite impedance at the entry to the cavity; therefore, a current ofthis kind cannot be engendered in the cavity.

To complete the decoupling effect between the two parts of the antenna,it is advantageous for the section 33 to have a length A equalling anodd number of quarter-waves at the frequency F i.e., the length k beingan integer. Theoretically, the impedance of the section 33 is then zero,or is very low in point of fact, at the frequency F The coupling betweenthe antennas is reduced still further by this minimum impedance inseries with the maximum impedance of the cavity 31.

This decoupling effect is desirable because, if the section 33 wereenergized by currents at the frequency F it would radiate in harmonicmode, that is to say that its radiation would run the risk of beingaimed at the zenith, or else of having several lobes separated by deadareas in the vertical plane. The presence of such dead areas ofradiation would be particularly unfavorable.

The currents having the frequency F flow outside the hollow conductor 31and along the section 33. The presence of the co-axial cavity having thelength B which is small compared to the wavelength at the base of thehigh frequency antenna is equivalent to the addition of a smallinductance in series, which is favorable as a rule, improving radiationat the frequency F FIG. 3 corresponds to an embodiment of the inventionproviding horizontal/horizontal polarization. The reference numeralsrepresent similarly designated elements in the system illustrated inFIG. 2. According to known methods, vertical polarization is transformedinto horizontal polarization by duplication of the antenna of FIG. 2,the parts G and D being identical to each other and identical to theantenna of FIG. 2.

The wire 34 is connected to the inner conductor 361 of a co-axial leadacting as a shared feeder for the two transmitters 11 and 13. Thesecondary windings 12s and 14s are connected to the outer conductor ofthis lead, which is marked 36e. The bases of the parts G and D of theantenna are connected to the secondary winding 37s of a matchedtransformer 37, whose primary winding 37p is connected to the extremityof the said co-axial lead.

The invention results in a particularly simple form of construction inthe case in which the ratio between the frequencies is equal orapproximately equal to 2:1, with P approximately equal to 2P and Aapproximately equal to 2x these two waves being polarized vertically.

In FIG. 4, which illustrates a diagrammatical section of a combinedantenna device in accordance with the invention, the latter comprisesbelow a ground potential zone 40, a co-axial feed line comprising anouter conductor 41 and a massive inner conductor 42. The upper portionof the inner conductor 42 is hollowed out into a cylindrical cavity 43whose upper portion 44 projects beyond the ground potential zone 40 by alength AD equal to a quarter of the wavelength X and this cavity 43 hasa total depth AG slightly greater than a quarter of the wavelength A forexample, exceeding a quarter of M by a length equal to a small fractionof the shorter Wavelength of the two, for example, smaller than 10% ofthe said shorter wavelength. The said cavity 43 contains a centralconductor 45 which projects beyond the upper rim of the cavity by alength AC equal to a quarter of A and which is inserted into the cavityto a depth equal to one quarter of A This central conductor is heldwithin the cavity 43 by any appropriate means, for example, by aninsulating ring 47.

The lower extremity of the co-axial feed line 41/42 may be connectedadvantageously to two generators 51 and 52, the one supplying thefrequency F and the other the frequency F through a duplexer 50, knownper se, of particularly simple type wherein the ratio between thefrequencies F and F supplied thereby is 2: 1. The device operates in thefollowing manner: For operation at the frequency F the impedance betweenthe elements 44 and 45 is zero in the plane 46 passing through theextremity A of the cavity, since the cavity 43 represents a quarter-waveopen at B. Everything evolves as though a radiating element having alength of one quarter of A; were present above the ground potential zone40.

For operation at the frequency F the impedance between the elements 44and 45 is infinite in the plane 46, since, the cavity 43 represents ahalf-wave open at B. Therefore, the currents in the element 44 do notflow into the element 45. This last element 45 moreover has a lowimpedance in the plane 46, which reduces the coupling between elements44 and 45 still further. The element 44 then acts as a quarter-wave unitof length AA; radiating above the ground potential zone 40.

The invention is equally applicable in the case in which the wavelengthsA and 1 have a ratio between them which is approximately equal to 2:1instead of being precisely equal to 2: l.

I have shown and described several embodiments in accordance with thepresent invention. It is understood that the same is not limited theretobut is susceptible of numerous changes and modifications as known to aperson skilled in the art and I, therefore, do not wish to be limited tothe details shown and described herein, but intend to cover all suchchanges and modifications as are encompassed by the scope of theappended claims.

I claim:

1. An antenna combination capable of operation on two very differentwavelengths A and M, the former being longer than the latter, comprisingat least one antenna section of the whip-type having a length ofsubstantially one-quarter of the wavelength A, for radiation of energyat the longer wavelength M, the end of said whip-type antenna sectionopposite to the free end thereof being formed by an antenna devicedimensioned to radiate energy at the short wavelength A in which a basememher of the said whip-type antenna section forming part of saidantenna device is connected to a balun having two symmetrical outletpoints of which each is connected to one of two further antenna sectionsof a length equal to substantially one-quarter of the shorter wavelengthA 2. The combination defined in claim 1, in which electrical energy issupplied by a first transformer whose primary winding is connected to ahigh-frequency transmitter and whose secondary winding is connected tothe conductors of a co-axial input lead on the said balun, and by asecond transformer whose primary winding is connected to a second lowerfrequency transmitter, and whose secondary winding is connected betweena ground potenital zone and a terminal of the secondary winding of thesaid first transformer, the two transmitters being arranged to operateat the same time.

3. The combination defined in claim 2 wherein said two further antennasections are coextensive with a line transverse to said whip-typeantenna and extend outwardly from the balun.

4. The combination defined in claim 2 wherein said balun comprises ahollow metal casing of a length A /2 and having said coaxial input leadprojecting axially there in to a length x /4.

5. The combination defined in claim 4 wherein said two further antennasections are connected to the respective conductors at the end of saidcoaxial input lead within said metal casing, said base member beingconnected between one conductor of said coaxial lead within said casingand the end wall of said casing opposite said coaxial lead.

6. An antenna combination capable of operation on two very differentwavelengths A and M, the former being longer than the latter, comprisingat least one antenna section of the whip-type having a length ofsubstantially one-quarter of the wavelength A for radiation of energy atthe longer wavelength M, the end of said whip-type antenna sectionopposite to the free end thereof being formed by an antenna devicedimensioned to radiate energy at the short wavelength A wherein saidwhiptype antenna section having an overall length equal substantiallyonequarter of the longer wavelength includes a base member connected toa hollow conductor short-circuited at the base end thereof, the lengthof the hollow conductor being close to one-quarter of the shorterwavelength A 7. The combination as defined in claim 6, in which thelength of portion of said antenna section projecting out of the saidhollow conductor is substantially equal to an odd number of quarters ofthe shorter wavelength 8. The combination defined in claim 7 furtherincluding a second antenna section of the whip-type including a basemember connected to a second hollow conductor short circuited at thebase end thereof, said one and said second whip-type antennas beingcoextensive with one another.

9. The combination defined in claim 8 including means for applyingenergy at the wavelength A alternately with energy at the wavelength Ato the short circuited base ends of said hollow conductors.

10. An antenna combination capable of operation on two very differentwavelengths x and A the former being longer than the latter, comprisingat least one antenna section of the whip-type having a length ofsubstantially one-quarter of the wavelength A for radiation of energy atthe longer wavelength M, the end of said whip-type antenna sectionopposite to the free end thereof being formed by an antenna devicedimensioned to radiate energy at the short wavelength x wherein theratio between the two wavelengths and A is close to 2: l, and furtherincluding a coaxial feed line Whose outer conductor terminates flushwith a ground potential zone and whose inner conductor projects beyondthe said ground potential zone by a length equal to substantially aquarter of the shorter wavelength )\2 to form said antenna device and ishollowed out to a depth slightly exceeding a quarter of the longerwavelength from its upper extremity forming a cylindrical cavity whichcontains a central conductor of an overall length of substantiallyone-quarter of the shorter wavelength A plus substantially one-quarterof the longer wavelength k said central conductor projecting beyond theupper rim of the said cylindrical cavity by substantially a quarter ofthe shorter wavelength A and being inserted into the said cavity to adepth of substantially one-quarter of the longer wavelength A 11. Thecombination defined in claim 10 wherein said central conductor issupported in said cylindrical cavity in spaced relation to said innerconductor.

12. The combination defined in claim 10 including means for energizingsaid coaxial feed line with energy at the wavelengths A and A at theratio 2:1 in the form of a duplexer.

References Cited UNITED STATES PATENTS 2,239,909 4/1941 Bushbeck et al.343-86l X 2,982,959 5/1961 Hanneken 343-730 X 3,426,351 2/1969 Hai etal. 343-730 X FOREIGN PATENTS 83 8,264 5/ 1960 Great Britain. 1,026,6444/ 1953 France.

HERMAN KARL SAALBACH, Primary Examiner M. NUSSBAUM, Assistant ExaminerUS. Cl. X.R. 343848, 853, 864

